Bicycles with electronic shifting systems and methods

ABSTRACT

Electronic shifting systems, mechanisms and methods of using the systems to operate a bicycle that allows front and rear gear changer mechanisms to be controlled with only two switches. The switches can be arranged so that each hand is only required to operate one switch to shift the bicycle.

BACKGROUND OF THE INVENTION

This present invention relates to bicycles and electronic shiftingsystems and methods of operating such systems.

Bicycles with prior art electronic shifting systems which use electricmotors to shift front and rear gear changers are known in the industry,but suffer from some deficiencies. For example, typically four buttonsare employed in prior art systems to operate front and rear gearchangers. These systems have a front gear changer upshift button, afront gear changer downshift button, a rear gear changer upshift button,and a rear gear changer downshift button. This arrangement requires eachhand to operate two buttons, typically with the right hand controllingthe rear gear changer buttons and the left hand controlling the frontgear changer buttons. A disadvantage of this kind of system is that itis easy for riders to accidentally press the wrong button when they arefocusing on the road ahead.

There is a demand, therefore, to provide a bicycle with a shiftingsystem that is effective and reduces or avoids unintended and/ormis-shifts. The invention satisfies the demand.

SUMMARY OF THE INVENTION

The invention is directed to electronic shifting systems, mechanisms andmethods of using the systems that allow both front and rear gear changermechanisms to be controlled with only two switches. The switches can bearranged so that each hand is only required to operate one switch toshift the bicycle. This eliminates the risk of accidentally actuatingthe wrong switch and simplifies shifting. For purposes of the invention,and unless specified otherwise, the term “switch” or “switch mechanism”will be understood to mean a single device, for example a button with anassociated set of contacts or a toggle with an associated set ofcontacts, the actuation of which (opening or closing) causes acontinuous or a momentary change of state, preferably in an electriccircuit, and not referring to a housing or the like containing aplurality of such devices. Actuation refers to the act of causing thechange of state of the switch and thus the system such that a signal isgenerated.

The invention generally includes a pair of handlebar mounted switchesused to control a bicycle electronic shifting system. In one embodiment,a first switch may be configured to shift a rear gear changer in anupshift direction and a second switch may be configured to shift therear gear changer in a downshift direction. No greater than two switchesare required for the system to produce all of the necessary signals andactions for controlling a bicycle with front and rear gear changers. Forpurposes of this application, downshift will be understood to mean theact of changing to a sprocket and producing less gear inches or, inother words using a rear gear shift scenario, shifting from a firstsprocket to a second sprocket, wherein the second sprocket has a largerdiameter than the first sprocket.

When both switches are operated at the same time or concurrently(overlapping in duration), a front gear changer is shifted from acurrent chainring to the other chainring of a two chainring system, forexample. In other words, if the switches are normally in an open state,if both switches are caused to be in a closed or an actuated stateconcurrently, the front gear changer is caused to perform a shiftoperation.

The switches can be mounted to opposite sides of the handlebar so thatone switch can be operated with the left hand and the other operatedwith the right hand. The switches can be mounted to the bar ends of atime-trial bicycle, inboard of the hand grips on a flat bar bicycle, orin a brake support structure typically used on drop-bar road bikes, forexample. Other suitable locations are contemplated by the inventionincluding the possibility of mounting two switches on the same part oradjacent parts of the bicycle structure.

Another advantage of the invention is that possibility of accidentallyshifting the front gear changer, a large gear change that could cause acrash if it happens unexpectedly, is greatly reduced because twoswitches must be actuated concurrently.

One aspect of the invention provides an electronic shifting system for abicycle including a first switch mechanism and a second switchmechanism. A control unit is in communication with and responsive tosignals from the first and second switch mechanisms. A front gear shiftmechanism is in communication with and responsive to command signalsfrom the control unit, wherein the control unit is configured todetermine when both the first switch mechanism and the second switchmechanism are actuated concurrently and responsively sends a front shiftcommand signal to the front gear shift mechanism to perform a front gearshift operation.

Another aspect of the invention provides an electronic gear shiftingsystem for a bicycle including a first switch mechanism and a secondswitch mechanism. A control unit is in communication with and responsiveto signals from the first and second switch mechanisms. A rear gearshift mechanism is in communication with and responsive to commandsignals from the control unit. Actuating the first switch mechanismsends a first signal to the control unit which is configured, inresponse to the first signal, to send a first command signal to the reargear shift mechanism to perform an upshift. Actuating the second switchmechanism sends a second signal to the control unit which is configured,in response to the second signal, to send a second command signal to therear gear shift mechanism to perform a downshift. A front gear shiftmechanism is in communication with and responsive to the command signalsfrom the control unit, wherein the control unit is configured todetermine when both the first switch mechanism and the second switchmechanism are actuated concurrently and responsively sends a front shiftcommand signal to the front gear shift mechanism to perform a front gearshift operation.

Yet another embodiment of the invention provides a method of shifting abicycle with an electronic gear shifting system, wherein the electronicgear shifting system includes a first switch mechanism, a second switchmechanism, a control unit in communication with and responsive tosignals from the first and second switch mechanisms, a front gear shiftmechanism and a rear gear shift mechanism, the front and rear gear shiftmechanisms in communication with and responsive to command signals fromthe control unit, including the steps of actuating the first switchmechanism to perform an upshift with the rear gear shift mechanism,actuating the second switch mechanism to perform a downshift with therear gear shift mechanism, and actuating both the first and secondswitch mechanisms concurrently to cause the front gear shift mechanismto perform a front gear shift operation.

Yet another aspect of the invention provides a method of shifting abicycle with an electronic gear shifting system, wherein the electronicgear shifting system includes a first switch mechanism, a second switchmechanism, a control unit in communication with and responsive tosignals from the first and second switch mechanisms, and a front gearshift mechanism in communication with and responsive to command signalsfrom the control unit, comprising the steps of determining with thecontrol unit that both of the first and second switch mechanisms areactuated concurrently, and performing a front gear shift operation withthe front gear shift mechanism.

It will be understood that the various signals from the switches andgenerated by the control unit(s) and so on, may take various forms. Forexample, signals from the switches may be individual or discreet orsomehow modified in certain circumstances, such as when both switchesare actuated concurrently (caused to be both in a changed state at thesame time or overlapping in duration). The signals may be the change ofstate of a circuit, or some other indication that the switch or circuitor circuitry has changed state such that the control unit can detect thechange of state and determine if and/or when some responsive action maybe generated.

These and other features and advantages of the invention will be morefully understood from the following description of one or moreembodiments of the invention, taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows a bicycle with drop-style handlebars incorporating anembodiment of the invention;

FIG. 2 shows a shift unit according to an embodiment of the invention;

FIGS. 3 and 4 show the invention adapted to be used on a flat handlebar,like that usable on a mountain bike;

FIG. 5 shows a diagram of front and rear gear changers and front andrear sprockets;

FIG. 6 a shows one embodiment of a gear change control unit according toan embodiment of the invention;

FIG. 6 b shows an alternate embodiment of a gear change control unit;

FIG. 7 shows a rear gear change mechanism according to an aspect of theinvention;

FIG. 8 shows a front gear change mechanism according to an aspect of theinvention;

FIG. 9 shows a flow chart illustrating a process control method for thecontrol unit according to an aspect of the invention;

FIG. 10 shows a flow chart illustrating a process control method for therear downshift method according to an aspect of the invention;

FIG. 11 shows a flow chart illustrating a process control method for therear upshift method according to an aspect of the invention;

FIG. 12 shows a flow chart illustrating a process control method for thefront shift method according to an aspect of the invention;

FIG. 13 shows a flow chart illustrating another embodiment of a processcontrol method for the control unit according to the invention employinga timer;

FIG. 14 shows a flow chart illustrating a rear shifter status storeroutine;

FIG. 15 shows another diagram of front and rear gear changers and frontand rear sprockets, wherein the front sprockets comprise 3 chainrings;

FIG. 16 shows a flow chart illustrating an embodiment of a front gearchange method; and

FIG. 17 shows yet another flow chart illustrating an embodiment of afront gear change method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the invention will herein be described withreference to the drawings. It will be understood that the drawings anddescriptions set out herein are provided for illustration only and donot limit the invention as defined by the claims appended hereto and anyand all their equivalents.

Referring to FIG. 1, the invention is shown adapted to a bicycle 20 withdrop-style handlebars 22, like that for a road or a cyclocross stylebike or the like. It will be understood that any suitable mountingarrangement of the system components is contemplated by the invention,the controls for which are preferably on the handlebar or on a handlebarassociated structure as depicted, or anywhere they can be accessed by auser. The shifting system 24, according to an embodiment of theinvention, may include a pair of shift units 26, mounted to thehandlebars 22. A control unit 28 is also shown mounted to the handlebars22. A front gear changer or front gear shift mechanism 30 may bepositioned on the seat tube 32 adjacent the front sprockets 34 so as toeffect gear changes to the front sprockets or an associated structure. Arear gear changer or rear gear shift mechanism 36 is mounted to a framemember 38 of the bicycle, such as a mount or rear dropout or anassociated structure as is known, in a position to effect gear changesto a rear sprocket 40. A communication link 42 is provided between thecontrol unit 28 and the shift units 26, the front gear changer 30, andthe rear gear changer 36. The system may also be applied, in someembodiments, to a bicycle where only a front or only a rear gear changeris used.

The control unit 28 is shown mounted to the handlebar 22, but could belocated anywhere on the bicycle 20 or, in the alternate, distributedamong the various components with routing of the communication link 42to accommodate the necessary signal and power paths. It would also bepossible to locate the control unit 28 other than on the bicycle, forexample on the user's wrist or in a jersey pocket, for example. Thecommunication link 42 could include wires or be wireless, or be acombination thereof.

One of the shift units 26 is shown in more detail in FIG. 2. It will beunderstood that a bicycle will preferably be provided with a pair ofshift units, or a number in an amount and positioned as desired. Forexample, a time trial bicycle may be provided with shift units on thebrake lever housings and another pair of modified shift units may beadapted to the time trial bar extensions. The shift unit 26 may includea brake support 44 mounted to the handlebar 22 and a brake lever 46pivotally mounted to the brake support. A switch mechanism 48 is mountedto the shift unit 26, and preferably in or on the brake support 44 andmay pivotally support a shift lever 50. The lever 50 may be permitted torotate inward in response to actuation of the brake lever 46 withoutoperating the switch mechanism 48. The switch mechanism 48 preferablyincludes a normally open contact switch (not shown) configured such thatthe switch closes or is actuated when the shift lever 50 is moved in aninward direction toward the center plane or center line (not shown) ofthe bicycle 20. Alternatively, a shift button 52 could be employed onthe brake support 44 or some other location on the shift unit 22 toactuate the switch mechanism 48.

The invention is not limited to the depicted placement or configurationof the switch mechanism 48; a signal can be generated by a button 52located on the brake support 44, brake lever 46, or handlebar 22, forexample, or by a shift lever pivotally connected to the brake support44, brake lever 46, or handlebar 22, for example. Other actuatingmechanisms may be employed to generate a signal to the control unit 28.The switch mechanism 48 could also be configured to be operated bypressing the brake lever 46 inward toward the center plane of thebicycle 20, for example.

In the alternate, while the invention contemplates operating theswitches to generate signals by closing the switch, e.g., closing anelectrical circuit, the invention also could be operated by actuating,operating or causing a switch to open, e.g., causing an open circuit orchanging the state of the mechanism and thus, the associated circuit.Furthermore, the switches could be optical or other types of switches,for example. The function of the switches are generally to permit theuser/operator to cause a change of state of the switch, and thuspotentially of the system, and generate a signal which the control unituses to detect and interpret an action of the user and generate anappropriate response or initiate an appropriate next step or number ofsteps.

Returning to FIG. 1, the drive unit 70 comprises a chain 72, frontsprocket assembly 34, which is coaxially mounted with a crank 74 havingpedals 76, and an electrically controlled front gear changer or gearchange mechanism 30, a rear sprocket assembly 40 coaxially mounted withthe rear wheel 78, and an electrically controlled rear gear changer orgear change mechanism 36.

The invention is shown on a mountain or comfort or urban style bicycle54 with flat style bars 56 in FIG. 3. It will be understood that thesystem 24 will be similar to that of the above described system withadaptations to the particular style of bicycle and its components. A topview of the mountain bicycle handlebar 56 is shown in FIG. 4. A leftshift unit 58 and right shift unit 60 are mounted to the handlebar 56.Each shift unit 58, 60 contains a button 52 that operates a switch (notshown) mounted to or within a respective shift unit.

The switch units 58, 60, control unit 28, front gear changer 62, and therear gear changer 64 are connected by a communication link 68. Thecommunication link 68 could be wired (as in the present example) orwireless, or a combination of each. The buttons 52 can be configured sothat the right button 52 b is actuated by the right hand, and the leftbutton 52 a is actuated by the left hand. The switches of each button 52a, 52 b can be configured to be normally open or normally closed. Theswitches in this example are preferably configured to be normally open,and will close momentarily when acted upon. It will be understood thatthe examples given herein are for the purpose of disclosing anembodiment of the invention without the intention of introducinglimitations that narrow the scope thereof.

Turning to FIG. 5 (and also referring to FIG. 1) the front sprocketassembly 34 may include two coaxially mounted chain rings, gears orsprockets F1-F2, and rear sprocket assembly 40 may include ten gears,cogs or sprockets R1-R10. The number of teeth on front sprocket F1 ispreferably less than the number of teeth on sprocket F2. The numbers ofteeth on rear sprockets R1-R10 typically gradually decrease from rearsprocket R1 to sprocket R10. Front gear changer 30 moves from a firstoperating position to a second operating position to move the chain 72between sprockets F1 and F2, and the rear gear changer 36 moves betweenten operating positions to switch the chain to one of rear sprocketsR1-R10. Preferably, a front gear position sensor 112 is used to sensethe operating position of the front gear changer 30, and a rear gearposition sensor 114 is used to sense the operating position of the reargear changer 36. Gear position sensors 112, 114 may comprise rotaryencoders, potentiometers, or other devices capable of sensing positionin a gear changer mechanism. Preferably, a battery 84 (FIG. 1), or morethan one battery, or some other power source powers the front and reargear changers 30, 36 as well as other electric components within thesystem.

The control unit 28 comprises a microprocessor that is programmed toreceive signals from the shifting system and responsively generatesignals to effect gear changes. One example of such a control unit 28 isshown diagrammatically at FIG. 6 a, which will be described in thecontext of the example shown in FIGS. 1 and 2, and includes acontroller, including a gear shift controller 100, a switch interpreter102, and a memory 141 to store a program (computer executable code) andoperational variables. The hardware that stores the program and performscomputer operations based on the instructions in the memory and signalsbeing generated by the various electronic components, such as theposition sensors and the switches includes a microcontroller orprogrammable logic device (PLD) or a similar component capable ofperforming the functions described herein.

The switch interpreter 102 monitors the switches in right and left shiftunits 27 a, 27 b and sends an appropriate command to the gear shiftcontroller 100 responsive to the request or input signal from the switchmechanism 48 of each of the units 27 a, 27 b. The front and rear gearchanger 30, 36 each comprises a motor 104, 106 that may include gearreduction (not shown), a motor driver 108, 110 for driving the motor,and a position sensor 112, 114 that senses the operating position of therespective gear changers. The gear shift controller 100 then generates acommand signal to move the appropriate gear changer 30, 36 to therequested operating position or gear in response to signals receivedfrom the shift interpreter 102 and the position sensor 112, 114.

In one illustrative example, the operation of the invention is asfollows. When the right switch 27 a is pressed, the rear gear changer 36performs an upshift, when the left switch 27 b is pressed the rear gearchanger 36 performs a downshift. When both right and left switches 27 a,27 b are pressed concurrently, the front gear changer 30 is shifted ortoggled between the two front sprockets 34, i.e. from one of to theother of the front sprockets.

Alternatively, the gear shift controller 100 in FIG. 6 a could bereplaced with a front shift controller 140 that includes amicroprocessor located in or associated with the front gear changer 130and a rear shift controller 142 that includes a microprocessor locatedin or associated with the rear gear changer 136 as shown in FIG. 6 b. Inthis embodiment the switch interpreter unit 102 would send gear shiftsignals to both the front shift controller 140 and rear shift controller142 when requested. The control system shown in FIG. 6 b could otherwisehave the same elements as that shown in FIG. 6 a.

As shown in FIG. 7, the rear gear changer 36 preferably includes a basemember 144 mounted to the bicycle frame 38 that houses a gear shiftmotor and gear mechanism 106, a link mechanism 146 pivotably connectedto the base member, and a movable member 148 pivotably mounted to thelink mechanism so that the movable member moves laterally relative tothe base member in accordance with the operation of the motor housedwithin the base member. Movable member 148 pivotably supports a chainguide 150 so that lateral movement of the movable member switches thechain 72 among rear sprockets 40 (R1-R10).

As shown in FIG. 8, the front gear changer 30 preferably includes a basemember 152 mounted to the seat tube frame member 32 of a bicycle thathouses a front gear shift motor 104, an output gear 154 coupled to thegear shift motor, a link mechanism 156 pivotably connected to the basemember and coupled to the output gear, and a movable chain guide member158 pivotably mounted to the link mechanism. Thereby, the movable chainguide member 158 moves laterally relative to the base member 152 inaccordance with the operation of the motor 104 associated with the basemember so that lateral movement of movable chain guide member 158switches the chain 72 among front sprockets 34 (F1-F2).

FIG. 9 is a flow chart of a first embodiment of the process control 200for control unit 28 or 128 of FIG. 6 a or 6 b, for example. It will beunderstood that where right and left switches are mentioned in thefollowing, the reference to right and left are for illustrativepurposes. Right and left could also be considered as first and secondswitches, for example, and thus it will be understood that thepositional reference is being used for purposes of clarity. In thealternate, the functions and/or positions of the left and right (firstand second) switches could be reversed either physically orelectronically.

In step S1, the control unit checks to see if the right switch 27 a isclosed. If it is determined that the switch 27 a is closed, at step S3the control unit 28 or 128 checks if the left switch 27 b is closed. IfYES, processing is moved to step S5 and the front gear changer 30 isshifted. If, at step S3, the left switch 27 b is open, processing movesto step S4 to check if the right switch 27 a is still closed. If theright switch 27 a is open, processing moves to step S6 and the rear gearchanger 36 is up-shifted. Once a right switch closed condition isdetected at step S1, the control unit 28 or 128 loops through stepsS3-S4 until either the right switch 27 a is released or the left switch27 b is pressed. Therefore, a rear gear changer upshift only occursafter pressing and releasing the right switch 27 a.

If the result of step S1 is NO, processing moves on to step S2 and thecontrol unit 28 or 128 checks if the left switch 27 b is closed. Theprocess is similar to the one described above except that when the leftswitch 27 b is open (released) without pressing the right switch 27 a,processing moves to step S7 and the rear gear changer 36 is downshifted.

FIG. 10 is a flow chart of a rear downshift routine 300. At step S8 theprocessor of the control unit 28 or 128 checks to see if the rear gearchanger 36 is in position 1 (i.e., aligned with the largest sprocket ofthe rear sprockets 40, which may also be referred to a first position orfirst end position). If the result is YES, the routine is exited withoutexecuting a downshift, as no further downshifts are possible. If theresult of S8 is NO, the process moves to step S9 and the rear gearchanger 36 is caused to downshift.

FIG. 11 is a flow chart of a rear upshift routine 400. At step S10 theprocessor checks to see if the rear gear changer 36 is in position 1(i.e., aligned with the smallest of the rear sprockets 40 also referredto as a last position or second end position). If the result is YES, theroutine is exited without executing an upshift, as no further upshiftsare possible. If the result of S10 is NO, the process moves to step S11and the rear gear changer 36 is caused to upshift.

FIG. 12 is a flow chart of a front shift routine 500. At step S12 thecontrol unit 28 or 128 processor checks to see if the front gear changer30 is in the position 2 (i.e., aligned with the larger of the twochainrings). If the result is YES, processing moves to step S14 and thefront gear changer 30 downshifts. If the result of step S12 is NO, thefront gear changer is upshifted. Therefore, every time a front shiftcommand is sent from step S5 the front gear changer will toggle betweenposition F1 and F2, the direction depending on which position it is ininitially.

FIG. 13 is a flow chart of a second embodiment 600 of the processcontrol for the control unit 28 or 128. A difference in this embodimentcompared with the embodiment shown in FIG. 9 is that when a singleswitch is operated, a rear upshift or downshift will be executed afteran elapsed time, without the need to release the switch.

When a single shift switch (e.g., one of 27 a or 27 b) is closed andheld, the operation is as follows: In step S20, the switches are readand the state of each (open or closed) is stored in memory 141. In stepS21, the system 28 or 128 checks if the state of any of the switches haschanged since the previous read. In this case since a single switch waspressed (closed) the processor moves to step S22 then on to step S23because a switch was closed. Since both switches were not closed,processing moves to step S24 the variable RS is assigned a rear shiftvalue (see FIG. 14 below: “STORE RS”). The initial value of the RSvariable upon program START is “null”.

FIG. 14 is a flow chart 700 of the STORE RS routine. RS can be a valuecorresponding to one of “upshift,” “downshift,” or “null.” In step S35the processor of control unit 28 checks the memory 141 to see if theright switch 27 a was closed during step S20 of the flow chart FIG. 13.If the result is YES, processing moves to step S36 and a valuecorresponding to “upshift” is assigned to variable RS. If the result ofS35 is NO, processing moves to step S37 where a value corresponding to“downshift” is assigned to variable RS. Processing then moves to stepS25 of FIG. 13 where a “pending timer” is started. The process movesback to step S20 to read the input switches, then to step S21 where theresult will be NO since the inputs have not changed.

Processing continues to loop through steps S26, S20, and S21 until thepending timer expires. Processing then moves to step S28 to check if arear shift value has been assigned to variable RS. Processing moves tostep S29 where the value of RS determines if the rear gear changer willupshift or downshift. If RS =“downshift”, processing moves to step S7where a rear downshift is executed, otherwise processing moves to stepS6 and a rear upshift is executed. From either of step S6 or step S7processing moves to step S30 where the value RS is cleared and set to“null” and processing continues back to step S20.

When the switch is opened (released) after the rear gear changer 36 hasshifted due to a “pending timer expired” condition the operation willcontinue as follows: Step S21 detects the switch open change andprocessing continues to step S22. Step S22 (switch closed?) will be NOand processing continues to step S27 (button released?) where a YESsends processing to step S28 (RS=null?). Since the value of RS was setto “null” immediately after a rear downshift or upshift in step S30, theresponse will be YES and processing continues back to step S20 and noadditional rear shift will occur.

However, if the switch was not opened (released) and a second switch wasclosed (pressed) after the rear gear changer 36 has shifted due to a“pending timer expired” condition the operation will continue asfollows: When the processor executes step S21 (switch changed since lastread?) the result will be YES and processing moves to step S22. Theresult of S22 (switch closed?) will be YES and processing continues tostep S23 (both switches closed?) where a YES result sends processing tostep S5 (shift front) and a front shift is executed. Therefore, if afirst switch is closed and held past the “pending timer” duration then asecond switch is closed, the system first shifts the rear gear changer36, and then shifts the front gear changer 30.

When a single shift switch is closed and opened before the pending timerexpires, the operation is as follows: In step S20 the input buttons areread and stored in memory 141. In step S21 the system checks if theswitches have changed state since the previous read. In this case, sincea switch was pressed, the processor will move to step S22 then on tostep S23. Since both switches were not closed processing moves to stepS24 where the variable RS is assigned a rear shift value. Processingmoves to step S25 where the pending timer is started. The process movesback to step S20 then to step S21 where the result will be NO.Processing continues to loop through steps S26, S20, and S21 until theswitch is opened or released. The change will be detected by step S21where the result will be YES and processing will continue to step S22.The result of step S22 (switch closed?) will be NO, processing moves tostep S27. The result of step S27 (switch opened?) will be YES, andprocessing will move to step S28 (RS =null?) to check if a rear shiftvalue been assigned to variable RS. Processing moves to step S29 wherethe value of RS determines if the rear gear changer will upshift ordownshift. If RS =“downshift”, processing moves to step S7 where a reardownshift is executed, otherwise processing moves to step S6 and a rearupshift is executed. From either steps S6 or S7 processing moves to stepS30 where the value RS cleared and set to “null” and processingcontinues back to step S20.

If a single switch is closed and a second switch is closed before the“pending timer” expires, the operation will be as follows: In step S21the system 28 checks if the switches 27 a, 27 b have changed since theprevious read, in this case since a switch was pressed the processorwill move to step S22 then on to step S23. Since both switches were notclosed just yet, processing moves to step S24 where the variable RS isassigned a rear shift value, depending on which switch was closed.Processing then moves to step S25 where the pending timer is started.The process moves back to step S20 then to step S21 where the resultwill be NO. Processing continues to loop through steps S26, S20, and S21until the second switch is closed. At this time the result of step S21will be YES and processing will move to step S22 where the result willbe YES and processing will continue to step S23 (both switches closed?).The result of step S23 will be YES and processing will move to step S5(shift front) and a front shift will be executed. Processing willcontinue to step S30 where RS is set to “null” and processing continuesback to step S20. When the switches are released processing willcontinue through steps S21, S22, S27 and S28. In step S28 (RS =null?)the result will be YES and processing will continue back to step S20 andtherefore no rear shifting will occur from the switch opening (release).

The shift interpreter 102 may also be programmed to allow multiple rearshifts if a single switch is held for a long duration. The presentinvention could also be adapted to shift three chainrings as follows:When a FRONT SHIFT routine is executed if the front gear changer is inthe large chainring position, then downshift. If the front gear changeris in the small chainring position, then upshift. If the currentchainring is the middle chainring the shift interpreter 104 can use ameasured parameter to determine whether an upshift or downshift isrequired, such as speed, acceleration, rear gear changer gear position,torque measured from a power meter, inclination of the road, amongothers. Another method to determine whether an upshift or downshift isrequested when shifting from the middle chainring would be to use the RSvariable that is set to the direction (upshift or downshift) of theswitch that was pressed first. For example, when an upshift is desiredfrom the middle chainring, the rider closes the right switch before theleft switch, indicating the desire to upshift.

Turning to FIG. 15 (and also referring to FIG. 1) the front sprocketassembly 234 may include three coaxially mounted sprockets F1-F2-F3, andrear sprocket assembly 40 may include ten sprockets R1-R10. The numberof teeth on front sprocket F1 is preferably less than the number ofteeth on sprocket F2, and the number of teeth of F3 is preferablygreater than the number of teeth on sprocket F2. The numbers of teeth onrear sprockets R1-R10 typically gradually decrease from rear sprocket R1to sprocket R10. Front gear changer 230 moves from a first operatingposition to a second operating position to move the chain 72 (FIG. 1)between sprockets F1 and F2 and from the second operating position to athird operating position to change to sprocket F3. The rear gear changer36 moves between ten operating positions, for example, to switch thechain to one of rear sprockets R1-R10. Preferably, a front gear positionsensor 112 is used to sense the operating position of the front gearchanger 230, and a rear gear position sensor 114 is used to sense theoperating position of the rear gear changer 36. Gear position sensors112, 114 may comprise rotary encoders, potentiometers, or other devicescapable of sensing position in a gear changer mechanism. Preferably, abattery 84 (FIG. 1), or more than one battery, or some other powersource powers the front and rear gear changers 230, 36 as well as otherelectric components within the system.

FIG. 16 shows a flow chart of another front shift routine 800. At stepS40 the control unit 28 or 128 processor checks to see if the front gearchanger 230 is in position 3 (i.e., aligned with the largest of thethree chainrings). If the result is YES, processing moves to step S14and the front gear changer 230 downshifts to F2. If the result of stepS40 is NO, the control unit 28 or 128 checks to see of the front gear isin the position 2 (i.e., aligned with the middle of the threechainrings). If the result is NO, processing moves to S13 and an upshiftis performed. If the result at S41 is YES, processing then checks to seeif the rear gear changer is aligned with a rear sprocket greater thanR5. If the result is NO, then a downshift is performed at S14.Conversely, if the result is YES, then an upshift is performed at S13.

The front shift method illustrated in FIG. 16 uses rear gear shiftposition criteria to determine how to shift the front gear changemechanism. This is an example of one criterion. Other criterion mayinclude: crank speed (pedaling cadence), bicycle wheel speed; increasingbicycle speed (acceleration) or decreasing bicycle speed (deceleration);pedaling torque; and bicycle inclination (uphill vs. downhill) forexample. Any of the above criteria may be determined and implemented inthe invention with well known sensors and processing devices.

FIG. 17 shows at 900 another front shift routine. At step S43 thecontrol unit 28 or 128 processor checks to see if the front gear changer230 is in position 3 (i.e., aligned with the largest of the threechainrings). If the result is YES, processing moves to step S14 and thefront gear changer 230 performs a downshift to F2. If the result of stepS43 is NO, the control unit 28 or 128 checks to see of the front gear isin the position 2 (i.e., aligned with the middle of the threechainrings). If the result is NO, processing moves to S13 and an upshiftis performed. If the result at S44 is YES, processing then checks at S45to see if RS equals “upshift,” (see FIG. 14). If RS does not equal“upshift” then processing moves to step S14 and the front gear changer230 performs a downshift (to F1). If RS equals “upshift” then processingmoves to S13 and an upshift is performed.

While this invention has been described by reference to a particularembodiment, it should be understood that numerous changes could be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to thedisclosed embodiment, but that it have the full scope permitted by thelanguage of the following claims. Also, where the claims do notexpressly state or necessarily imply the sequence of all or some steps,it would cover the steps performed in any order or simultaneously.

1. An electronic shifting system for a bicycle, comprising: a firstswitch mechanism; a second switch mechanism; a control unit incommunication with and responsive to signals from the first and secondswitch mechanisms; and a front gear shift mechanism in communicationwith and responsive to command signals from the control unit, whereinthe control unit is configured to determine when both the first switchmechanism and the second switch mechanism are actuated concurrently andresponsively sends a front shift command signal to the front gear shiftmechanism to perform a front gear shift operation.
 2. The electronicshifting system of claim 1, further comprising a rear gear shiftmechanism in communication with and responsive to signals from thecontrol unit; wherein the control unit is configured to determine ifboth of the first and second switch mechanisms are not actuatedconcurrently, and responsively sends a rear shift command signal to therear gear shift mechanism to perform a rear gear shift operationdependent upon which of the first and second switch mechanisms areactuated.
 3. The electronic shifting system of claim 2, wherein the reargear shift operation is performed after expiration of a predeterminedtime period.
 4. The electronic shifting system of claim 2, wherein therear gear shift operation is performed if one of the first and secondswitch mechanisms is actuated and then non-actuated before theexpiration of a predetermined time period.
 5. The electronic shiftingsystem of claim 1, further comprising a front gear position sensor forsensing a current gear position of the front gear shift mechanism,wherein the control unit is configured to send the front shift commandsignal to move the front gear shift mechanism a direction to perform afront gear shift operation depending on the sensed current gearposition.
 6. The electronic shifting system of claim 1, wherein thefront gear shift mechanism includes two gear positions.
 7. Theelectronic shifting system of claim 1, wherein the front gear shiftmechanism includes three gear positions.
 8. A method of shifting abicycle with an electronic gear shifting system, wherein the electronicgear shifting system comprises a first switch mechanism, a second switchmechanism, a control unit in communication with and responsive tosignals from the first and second switch mechanisms, and a front gearshift mechanism in communication with and responsive to command signalsfrom the control unit, comprising the steps of: determining with thecontrol unit that both of the first and second switch mechanisms areactuated concurrently, and performing a front gear shift operation withthe front gear shift mechanism.
 9. The method of shifting a bicycle withan electronic gear shifting system of claim 8, wherein the front gearshift mechanism performs the front gear shift operation between two gearpositions.
 10. The method of shifting a bicycle with an electronic gearshifting system of claim 8, wherein the front gear shift mechanismperforms the front gear shift operation between three gear positions.11. A method of shifting a bicycle with an electronic gear shiftingsystem, wherein the electronic gear shifting system includes a firstswitch mechanism, a second switch mechanism, a control unit in operativecommunication with and responsive to signals from the first and secondswitch mechanisms, and a front gear shift mechanism in operativecommunication with and responsive to command signals from the controlunit, comprising: monitoring with the control unit if one of the firstand second switch mechanisms is actuated; sensing when one of the firstand second switch mechanisms is actuated; determining if the other ofthe first and second switch mechanisms is actuated if the one of thefirst and second switch mechanisms is actuated; generating a front shiftcommand signal with the control unit if the first and second switchesare determined to be actuated concurrently; and performing a front gearshift operation with the front gear shift mechanism responsive to thefront shift command signal.
 12. A method of shifting a rear derailleurof a bicycle with an electronic gear shifting system, wherein theelectronic gear shifting system includes a first switch mechanism, asecond switch mechanism, a control unit in operative communication withand responsive to signals from the first and second switch mechanisms,the rear gear shift mechanism in operative communication with andresponsive to command signals from the control unit, comprising:monitoring with the control unit if one of the first and second switchmechanisms is actuated; sensing when one of the first and second switchmechanisms is actuated; determining if the other of the first and secondswitch mechanisms is actuated if the one of the first and second switchmechanisms is actuated; disregarding the control unit if the first andsecond switches are actuated concurrently; determining which of thefirst and second switches is actuated if only one of the first andsecond switch mechanisms is actuated; generating a rear shift commandsignal with the control unit indicative of said determining of which ofthe first and second switches is actuated; and performing a rear shiftoperation with the rear gear shift mechanism according to the rear shiftcommand signal.
 13. The method of shifting a rear derailleur of abicycle of claim 12, wherein the control unit is distributed among thecomponents of the electronic gear shifting system.
 14. The method ofshifting a rear derailleur of a bicycle of claim 12, wherein the controlunit is not distributed among the components of the electronic gearshifting system.